When a straight or extension ladder is positioned against a structure, it is essential that the ladder be properly angled to prevent slipping of the ladder feet. As a general rule, the base of the ladder should be positioned at a distance which is one-fourth of the working length thereof from the vertical support. If such positioning is not possible, the top and bottom of the ladder should be braces, tied, or otherwise secured for safety. This general rule, however, assumes that the base of the ladder is positioned on a level surface. This assumption is often not true in practice. When a ladder is positioned on a sloping surface, such as a roof, the angle between the ladder and the support surface is decreased from that when the surface is level with a corresponding decrease in the frictional holding ability of the ladder feet and, accordingly, a greater risk of the ladder slipping when in use.
Indicators, such as those shown in U.S. Pat. No. 2,845,719, Thomiszer, and U.S. Pat. No. 3,118,234, Wilson, have been provided for showing the angular orientation of the ladder but such devices do not take into account the possibility that the ladder will be used on a non-level surface. Similarly, the warning labels provided in American National Standard A14.5-1981 do not provide guidance for the safe use of ladders on sloping surfaces.
It is, accordingly, the primary object of the present invention to provide a safety indicator for a single or an extension ladder which is equipped with an articulated foot that provides a clear indication as to whether the ladder is safely positioned or requires blocking, tieing or the like for said use whether on a level or a sloping surface.
A further object of the invention is the provision of such a ladder safety indicator which may be applied to new or existing ladders without requiring modification of the ladder structure.